In prior art carrier demodulation of shift keyed signals, such as biphase shift keyed (BPSK), quadra-phase shift keyed (QPSK), offset quadra-phase shift keyed (O-QPSK), minimum shift keyed (MSK), serial minimum phase shift keyed (SMSK), etc., the carrier demodulator includes a voltage controlled oscillator which is continuously adjusted into phase with the incoming carrier by a phase locked loop. Typical examples of this type of demodulator are illustrated and described in U.S. Pat. No. 3,768,030, entitled "Automatic Signal Acquisition Means For Phase Lock Loop With Anti-Sideband Lock Protection", issued Oct. 23, 1973; U.S. Pat. No. 3,806,822, entitled "Phase Locked Loop Employing Alternating Current Injection for Fast Synchronization", issued Apr. 23, 1974; U.S. Pat. No. 4,085,378, entitled "QPSK Demodulator", issued Apr. 18, 1978, and U.S. Pat. No. 4,188,589, entitled "Automatic Signal Acquisition Means For a Phase Locked Loop With Anti-Sideband Lock Protection", issued Feb. 12, 1980. Conventional phase locked loops cannot be made to acquire rapidly with 100 percent certainty because of the quasi stable lock point at 180.degree.. Various attempts have been made to improve the probability of lock by shaping the phase detector transfer function, injection locking, loop bandwidth variation, etc. These methods provide one to two orders of magnitude improvement, but normally require a significant additional circuit complexity.